Medium rugged twill field bag by Filson Navy (Blue) Rugged twill small field bag by Filson Black (Black) Filson Rugged Twill XS Field Bag Black Rugged twill small field bag by Filson Black (Black). The XS Field Bag is a smaller, lined version of one our earliest Rugged Twill Bags. The heavy duty fabric from Englands British Millerain is legendary for its durability and lightly waxed for weather resistance. Carried cross body, it rides neatly at the hip or in the small of the back. The interior is lined with cotton canvas, with a zippered security pocket. Leather tabs snug the top opening to help keep gear secure. The large rain flap is secured with a leather strap and brass buckle. A roller in the buckle helps minimize wear on the strap. The bag's Bridle Leather has been slowly vegetable tanned in natural plant based solutions. Exterior full width stock pocket. Removable shoulder strap.